1. Field of the Invention
Example embodiments of the present invention are directed generally to a power source switching apparatus and method thereof, and more particularly to a power source switching apparatus and method of providing power.
2. Description of the Related Art
A portable mobile device may be used in places where an external power source voltage may not be available because the portable mobile device may be configured to operate with an internal power source voltage applied by a battery. Portable mobile devices may be configured to use rechargeable batteries and/or disposable batteries. Rechargeable batteries may typically be charged by external power source voltages. A charge capacity of rechargeable batteries may typically be relatively limited, and therefore rechargeable batteries may need to be recharged from time to time as charges stored therein are exhausted.
For example, a user may charge a rechargeable battery during a period where the portable mobile device may be powered by an external power source voltage. In other words, the portable mobile device may draw power from the external power source to both power the portable mobile device as well as charge the rechargeable battery.
FIG. 1 is a block diagram illustrating a conventional portable mobile device. Referring to FIG. 1, the portable mobile device may include a voltage drop diode 120, a controller 130, a battery charger 140, a battery 150, a direct current (DC)-DC converter 160, a system load 170, and a switch SW1.
Referring to FIG. 1, the voltage drop diode 120 may be used if charges are supplied to the battery 150 via the battery charger 140 while the portable mobile device is powered by an external power source 110. An operating voltage of the system load 170 may be lower than a voltage of the external power source 110 in order to reduce power consumption of the system load 170. Accordingly, the voltage of the external power source 110 may be reduced or dropped using at least one voltage drop diode 120 connected in series, and the reduced voltage may then be supplied to the system load 170. The controller 130 may generate a control signal CON for selecting one of the voltage of the external power source 110 (e.g., applied through the voltage drop diode 120) and the voltage of the battery 150.
Referring to FIG. 1, the battery charger 140 may charge the battery 150 using the external power source 110. During charging, the battery 150 may receive charges from the battery charger 140. The battery 150 may output a voltage corresponding to a voltage level at which the battery 150 is charged. The switch SW1 may supply one of the output voltage of the battery 150 and the output voltage of the voltage drop diode 120 to the DC-DC converter 160, in response to the control signal CON output from the controller 130. The DC-DC converter 160 may convert the voltage supplied through the switch SW1 into a voltage having a level which may be sufficient to power the system load 170. The system load 170 may indicate a functional block which may perform a specific function using the voltage supplied from the DC-DC converter 160.
FIG. 2 is a block diagram illustrating another conventional portable mobile device. Referring to FIG. 2, the output voltage of a voltage drop diode 220 may be directly supplied to a system load 270 through a switch SW2, and the output voltage of a battery 250 may be supplied to a DC-DC converter 260 through a second switch SW3. The two switches SW2 and SW3 may be controlled by a control signal CON output from a controller 230 and a signal which may be obtained by inverting a phase of the control signal CON through an inverter 280, respectively. Accordingly, the first switch SW2 and the second switch SW3 may be turned on and off, respectively, or vice versa.
The conventional portable mobile devices illustrated in FIGS. 1 and 2 may each have (i) a battery mode in which the portable mobile device may be powered by a battery and (ii) an external power source mode in which the battery may be charged via the external power source while the portable mobile device is either operating via the external power source or not operating. During a transition between the battery mode and the external power source mode (e.g., in response to plugging in or unplugging the portable mobile device), a voltage supplied to the DC-DC converter 160 or the system load 270 may change at a relatively high rate.
FIGS. 3A, 3B and 3C illustrate a supplied voltage during a first transition from a battery mode to an external power source mode and a second transition from the external power source mode back to the battery mode. In an example, the supplied voltage illustrated in FIG. 3 may represent a voltage applied to the DC-DC converter 160 and/or the system load 270.
FIG. 3A illustrates a theoretical voltage level fluctuation of the power source voltage applied during a transition between the battery mode and the external power source mode. The theoretical voltage level of FIG. 3A is not intended to represent a capability of the conventional art, but is rather intended to illustrate a conceptual “ideal” voltage transition having a linear or “smooth” voltage change during a power source transition.
Referring to FIG. 3A, in a battery mode Bat_mode, a level of the power source voltage applied to the system may gradually be reduced over time. The external power source mode Recharge_mode for charging may be initiated before the voltage reaches a lower threshold voltage VRL. In the external power source mode Recharge_mode, the voltage of the battery may increase, and the external power source mode Recharge_mode may be switched to the battery mode Bat_mode before the voltage reaches a higher threshold voltage VRH. In an example, the lower threshold voltage VRL may represent a minimum voltage level required to power the portable mobile device and the higher threshold VRH may represent a voltage level above which the portable mobile device may not be capable of safe operation.
However, in a real-world environment, the external power source may have a voltage level at least equal to the lower voltage VRH because, typically, a voltage used to charge a battery may be set to a voltage level higher than a voltage level to which the battery is configured to be charged. Hereinafter, it may be assumed that the external power source voltage may be set to Vpp.
FIG. 3B illustrates a conventional voltage level fluctuation of the power source voltage applied during a transition between the battery mode and the external power source mode.
Referring to FIG. 3B, in the instant when the battery mode is switched to the external power source mode or the instant when the external power source mode is switched to the battery mode, a voltage level of the external power source voltage may spike (e.g., rapidly change). Furthermore, because the power source voltage may be set to Vpp, which may be higher than the lower voltage VRH, in the external power source mode Recharge_mode, the battery may be charged by the power source voltage Vpp but the power source voltage Vpp may be too high to safely supply power to the portable mobile device. Accordingly, the portable mobile device may be inoperable during battery charging because the voltage used to charge the battery may be unsuitable to power the portable mobile device.
FIG. 3C illustrates another conventional voltage level fluctuation of the power source voltage applied during a transition between the battery mode and the external power source mode.
Referring to FIG. 3C, if the external power source voltage is reduced to the same voltage as the lower voltage VRH using a plurality of voltage drop diodes which are connected to each other in series, the power source voltage (e.g., set to VRH) may be supplied to a system load of the portable mobile device. Accordingly, because the external power source voltage may be maintained at the lower voltage VRH, the external power source voltage may be applied to the system while the battery is charged (e.g., although the charging of the battery may take a longer period of time due to the lower charging voltage). However, in FIG. 3C, similar to FIG. 3B, in the instant of switching the battery mode to the external power source mode or switching the external power source mode to the battery mode, the power source voltage may spike or change rapidly, thereby degrading a performance of the portable mobile device.